The invention is based on an apparatus for synchronizing the rpm of drive wheels upon starting of a motor vehicle, equipped with a pressure-fluid-controlled brake system, in which the synchronizing is performed by applying a metered brake pressure to the drive wheel having the higher rpm.
In a known starting aid of this type (see the journal Fluid, January, 1984, p. 11), the final control element is embodied as a diaphragm motor, which is triggered with an air pressure or vacuum derived from the control signal and via drive members coupled with the diaphragm actuates one or the other control piston of the brake pressure controllers aligned with one another. This kind of final control element is relatively slow and requires a rather large air or vacuum reservoir, which in the case of Diesel engines necessitates a separate vacuum pump.
In another known apparatus of this generic type (British Pat. No. 2,128,278), the final control element comprises two electromagnets, on each of the armatures of which a respective control piston of each of the two brake pressure controllers is supported, under the influence of its restoring spring. The control signals are supplied as an exciter current, in accordance with a positive or negative rpm difference, to one or the other electromagnet, thereby displacing the associated control piston in the direction for decreasing the volume defined by it and thus feeding a brake pressure into the wheel brake cylinder connected with it. The heavy electromagnets required for this kind of final control element allow only a relatively slow armature motion, so that only a sluggish control of brake pressure is attainable.